POS0263 PREVALENCE OF OCCIPITAL PROTUBERANCE ENTHESOPHYTE IN NON-INFLAMMATORY AND INFLAMMATORY RHEUMATIC DISEASES: SANZ SIGN
Authors: N. De la Torre Rubio, J. Campos, M. Pavía Pascual, M. Machattou, P. Navarro Palomo, M. Alonso de Francisco, C. Navarro Joven, C. Merino Argumánez, B. Garcia-Magallon, M. Fernandez Castro, H. Godoy, C. Barbadillo Mateos, C. Isasi Zaragoza, L. F. De Villa, J. L. Andréu Sánchez, J. Sanz
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> The exostosis of occipital protuberance was described recently in non-inflammatory processes<sup>[1]</sup>. Despite of enthesophytes are usually seen in radiographs of older asymptomatic population, in the last few years the presence of occipital protuberance enthesophyte (OPE) has been observed frequently in young patients, with a prevalence of 41% in adults younger than 30-year-old<sup>[2]</sup>. To our knowledge OPE has not been described in inflammatory rheumatic diseases. <h3>Objectives</h3> To determine the prevalence of OPE in non-inflammatory processes (NIP), psoriatic arthritis (PsA), spondyloarthritis (SpA) and rheumatoid arthritis (RA). <h3>Methods</h3> Retrospective descriptive and comparative study of cervical radiographs randomly collected from patients older than 18 years old attended in a rheumatology consult of a tertiary hospital from July 2022 to January 2023 until 30 patients per group were completed (total of 120 patients). We classified patients in four groups by diagnosis: NIP (traffic accident and spine surgery excluded), PsA, SpA and RA. The following variables were collected: sex, age at the time of radiograph was performed, OPE (yes/no) evaluated by a senior rheumatology resident (4 years of experience) and by a senior rheumatologist (25 years of experience). Descriptive statistics were used for the presentation of the results and Cohen's Kappa coefficient was calculated to quantify the degree of agreement in the diagnosis of enthesophyte presence between both rheumatologists. Chi square test with Yates correction was performed to compare sex and prevalence between groups and ANOVA to compare mean age. <h3>Results</h3> A total of 120 patients were collected, 30 patients per group. Seventy point eight per cent were women; mean age was 58.5 years with a standard deviation of 15. The groups were homogeneous (sex was performed by Chi Square test, p &lt; 0.0001; mean age was performed by ANOVA, p = 0.006). Sixty-one of 120 patients (51 %) had OPE (23 % in non-inflammatory group, 60 % in inflammatory group); OPE prevalence was statistically significant in inflammatory diseases (p &lt; 0.001). Stratified analysis by sex (p = 0.2) and age (p = 0.06) between inflammatory and non-inflammatory pathology showed no differences, although incidence of OPE in non-inflammatory processes tends to increase with older age. Results by group are shown in <i>Table 1</i>. <i>Figure 1</i> shows different types of enthesophyte morphology. The global degree of agreement according to Cohen's Kappa index was 0.8, representing 89 % agreement (substantial degree); the best degree of agreement was obtained in SpA (Cohen's Kappa index 0.9, representing 97 % agreement, almost perfect degree). <h3>Conclusion</h3> To our knowledge this is the first study about the prevalence of OPE in inflammatory and non-inflammatory rheumatic diseases, being more prevalent in inflammatory diseases 60 % (p &lt; 0.001), especially in spondyloarthritis and psoriatic arthritis. The global degree of agreement between a senior rheumatology resident and a senior rheumatologist was substantial, being almost perfect in spondylarthritis. We will conduct a new study to find out whether different morphology of occipital enthesophytes is associated to any inflammatory rheumatic disease. <h3>References</h3> [1]Singh R. Bony tubercle at external occipital protuberance and prominent ridges. J Craniofac Surg. 2012 Nov;23(6):1873-4. [2]Shahar D, Sayers MG. A morphological adaptation? The prevalence of enlarged external occipital protuberance in young adults. J Anat. 2016 Aug;229(2):286-91. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.